4-(tetrahydropyran-2&#39;-yloxy)-pentyl-phosphonates

ABSTRACT

PREPARATION OF A,B-UNSATURATED CARBOXYCLIC KETONES BY REACTING AN ENOL LACTONE WITH A CARBANION GENERATED BY TREATMENT OF A METHYLPHOSPHONATE OR A MONO-SUBSTITUTED METHYLPHOSPHONATE WITH BASE.

United States Patent 3,639,428 4-(TETRAHYDROPYRAN-2'-YLOXY)-PENTYL- PHOSPHONATES John H. Fried, Palo Alto, Calif, assiguor to Syntex Corporation, Panama, Panama N0 Drawing. Filed Dec. 4, 1967, Ser. No. 687,502 Int. Cl. C07f 9/40 US. Cl. 260-3453 2 Claims ABSTRACT OF THE DISCLOSURE Preparation of a,fi-unsaturated carbocyclic ketones by reacting an enol lactone with a carbanion generated by treatment of a methylphosphonate or a mono-substituted methylphosphonate with base.

The present invention relates to the production of unsaturated carbocyclic ketones.

More particularly, this invention relates to a novel process which has general utility for the conversion of enol lactones into O B-unsaturated carbocyclic ketones.

The expression enol lactone, as used herein, refers to an unsaturated lactone having a,/3-ethylenic unsaturation in respect to the heterocyclic oxygen atom. The expression p-unsaturated carbocyclic ketone, as used herein, refers to a carbocyclic ketone having a,B-ethylenic unsaturation in respect to the -keto group.

Prior to the present invention, enol lactones were converted into u,B-unsaturated carbocyclic ketones by a twostep process which involved reacting the enol lactone with about one equivalent of a Grignard reagent, for example, methylmagnesium chloride, to open the lactone ring and thereafter the thus-obtained diketonic intermediate product was cyclized by treatment with acid or alkali to obtain the carbocyclic ketone. See, for example, US. Pats. 3,057,907 and 3,321,489 and French Pat. 1,359,675. In addition to the disadvantage that the conversion of enol lactones into carbocyclic ketones requires at least two steps, prior methods are often difiicult to control, unsuitable for -membered ring systems, and of very narrow utility in that the et-unsaturated carbocyclic ketones obtainable are very limited.

A primary object of the present invention, therefore, is to provide a process for the production of u,B-unsaturated carbocyclic ketones from enol lactones which overcomes the aforementioned disadvantages. Another object of the present invention is to provide a process for the production of a,B-unsaturated carbocyclic ketones which is economical and simple to operate but yet of great flexibility or adaptability in respect to the type of afiunsaturated carbocyclic ketone that can be produced. Another object of this invention is to provide a singlestep process for the production of L B-unsaturated carbocyclic ketones. Still another object of the present invention is to provide a process for the production of a,B-unsaturated carbocyclic ketones which is useful in the total synthesis of steroids and to novel intermediates therefor. Other objects, advantages and meritorious features of the present invention will become apparent as the invention is described in more detail hereinafter.

In accordance with the foregoing objects of the present invention, there has been discovered a very versatile process for the production of 0:,fi-HI1S3tl1lflt6d carbocyclic ketones which comprises reacting, under substantially anhydrous conditions in an organic solvent inert to the reaction, an enol lactone with a carbanion generated by the reaction of base with a phosphonate selected from the group consisting of methylphosphonates and monosubstituted methylphosphonates.

The process of the present invention is applicable to the conversion of enol lactones into a s-unsaturated carbocyclic ketones in general. The enol lactone can be either a monocyclic enol lactone or a polycyclic compound such as bicyclic, tricyclic and tetracyclic enol lactones depending upon the u,;3-unsaturated carbocyclic ketone desired to be obtained. The process of the present invention is particularly suitable for enol lactone starting materials wherein the heterocyclic ring thereof contains at least 5 members and mono-ethylenic unsaturation. The enol lactones which can be converted into age-unsaturated carbocyclic ketones by the process of this invention are too numerous to list. Exemplary of the monocyclic and polycyclic enol lactones which can be used in the process of the present invention are zit-angelica lactone, A -valeryl lactone, isocoumarin, 3-methyl-6,8-dimethoxyisocoumarin, 3-phenylisocoumarin, 3-benzoyl-7,S-dimethoxyisocoumarin, 3-chloroisocoumarin, benzal phthalide, 5,6,7-trimethoxyisocoumarin, fi-lactone of lB-hydroxy-2fi-methy1-2a- (2'-carboxyethyl)-3-hydroxycyclopent-3-ene, fi-lactone of lfl-hydroxy 4 (2'-carboxyethyl)-5-hydroxy-7aB-methyl-3aa,4fl,7,7a-tetrahydroindane, 4-oxa 17B acetoxyandrost-5-ene-3-one, 3 ethoxy-l7-oxa-D-homoestra-l,3,5- (10), 15-tetraen-17-one, 4-oxa-cholest-5-en-3-one, 17,20; 20,2l-bismethylenedioxy 4 oxa-l lB-hydroxypregn-S-en- 3-one, and 3-methoxy-16-oxaestra-1,3,5 l0),8,l4-pentaen 17-one.

The phosphonates which are useful in the production of tam-unsaturated carbocyclic ketones in accordance with the process of the present invention are the methylphosphonates and mono-substituted methylphosphonates. Methylphosphonates and mono-substituted methylphosphonates useful in the present invention are illustrated by the following Formulas A and B, respectively:

CHa R)2 R CH2--P(OR)2 wherein R is selected from the group consisting of substituted and unsubstituted, saturated and unsaturated, aliphatic, carbocyclic and carbocyclic-aliphatic radicals and R is selected from the group consisting of substituted and unsubstituted, saturated and unsaturated, aliphatic, carbocyclic and carbocyclic-aliphatic radicals.

Phosphonates of Formulas A and B above can be prepared, for example, by the reaction of a di-substituted phosphite (C) with an organic halide or sulfonate of the Formulas D and E, respectively, in the presence of a base, e.g. sodium hydride,

In the above formulas, R and R are as defined above and X is chloro or bromo or OSO R wherein R is alkyl or aryl. The formation of the phosphonates can be carried out in inert solvents such as ether, tetrahydrofuran, monoglyme, diglyme, or dioxane and preferably in an oxygen-free atmosphere. The method of preparing the phosphonates is not part of the present invention. A suitable procedure for the formation of methylphosphonates and mono-substituted methylphosphonates useful in the prsent invention is to react a di-substituted phosphite of Formula C with an organic halide or sulfonate of Formulas D and E in an inert solvent in the presence of about one equivalent of a base such as sodium hydride under an inert atmosphere at a temperature of about 10 C. to about room temperature. Other methods are described in, for example, US. Pat. 2,754,319.

While the methylphosphonates and mono-substituted methylphosphonates which can be employed in the process of the present invention are too numerous to list here, they can be exemplified by the following:

dimethyl methylphosphonate dimethyl ethylphosphonate diethyl benzylphosphonate diethyl methylphosphonate dicyclohexyl methylphosphonate diphenyl methylphosphonate di-(n-butyl) methylphosphonate dibenzyl methylphosphonate diethyl methylphosphonate diethyl 4,4-dimethoxybutylphosphonate diethyl 4,4-ethylenedioxypentylphosphonate dimethyl 4,4-dimethoxy-3-methylbut-Z-enylphosphonate diethyl 4-chloropent-3enylphosphonate diethyl 4-(tetrahydropyran-2'-yloxy)pentylphosphonate diethyl 4,4-ethylenedioxy-3methylpentylphosphonate di(methoxyethyl) methylphosphonate di(2-ethylhexyl) methylphosphonate di(n-octyl) ethylphosphonate di(ethoxyethyl) methylphosphonate In the practice of the process of the present invention, a phosphonate of Formula A or B is reacted with a base to generate the corresponding carbanion of the Formulas A and B, respectively:

Because of the general instability of the phosphonate carbanion, it is necessary that the reaction between the phosphonate and base be carried out at low temperatures of the order of about -150 C. to about C., preferably about 100 C. to about 40 C. After formation of the carbanion is complete, the low temperature of the reaction mixture is maintained during the addition of the enol lactone and thereafter the cooling means removed or otherwise raising the reaction temperature to about room temperature. Suitable bases for generating the carbanion include organo alkali metal compounds such as n-butyl lithium, phenyl lithium, methyl sodium, sodium acetylide, methyl potassium, methyl lithium, tolyl lithium, methyl potassium lithium pyridide, and the like; alkali metal hydrides such as sodium hydride, potassium hydride or lithium hydride; alkali metal amides such as sodamide, and the like.

In practicing the conversion of an enol lactone into the corresponding a s-unsaturated carbocyclic ketone in accordance with the process of the present invention, the reaction is carried out using about equal molar amounts of the phosphonate, base and enol lactone. More than one molar equivalent of the phosphonate and base can be used but it is generally disadvantageous to do so because the excess reagent may react further with the carbonyl group of the desired carbocyclic ketone. Thus, it is preferred to use about one molar equivalent of the phosphonate and base or a modest excess of each such as up to about 1.2 molar equivalents. Any organic solvent can be used for the reaction medium so long as it is inert to the reaction and liquid at the reaction temperature being used. Suitable organic solvents include ether, tetrahydrofuran, dioxane, monoglyme, diglyme, and the like. The reaction between the carbanion and enol lactone generally goes to completion in from about 0.5 hour to about 48 hours depending upon such factors as temperature and the relative reactivity of the carbanion and the enol lac- .tone. The reaction temperature can vary from about 150 C. to about room temperature, preferably about --100 C. to about room temperature depending upon such factors as the stability of the carbanion, the relative reactivity of carbanion and enol lactone being reacted and the time in which it is desired to complete the reaction. After formation of the carbanion is complete and the enol lactone has been introduced, the reaction mixture can be permitted to rise to about room temperature in order to complete the reaction in a shorter period of time. Depending upon the stability of the particular carbanion being used, the reaction mixture can be heated above room temperature, for example reflux temperature, if still shorter reaction times are desired. However, because of the general instability of the carbanion, the reaction between the phosphonate and base must be carried out at low temperatures of the order of about C. to 20 C. For optimum results, it is important that the reaction be conducted under as near anhydrous conditions as possible and preferably under an inert oxygenfree atmosphere such as nitrogen, argon, and the like. While the concentration of the enol lactone and carbanion does not appear to be critical, it is preferred to operate at low concentrations of the order of about two to about twenty-five percent by weight of the reaction medium. The foregoing reaction conditions are largely dependent upon the particular phosphonate, base and enol lactone employed and are presented as a guide. Provided with the foregoing and the examples hereinafter, the most advantageous or optimum conditions and proportions of the enol lactone, phosphonate and base for a particular (1,13- unsaturated carbocyclic ketone are easily determinable by one of ordinary skill in the art using routine experimentation.

In the case of enol lactone starting materials having other carbonyl groups present, e.g. an isolated keto group, it is preferable to introduce a protecting group prior to the reaction. In general, the phosphonate anions tend to react faster with the enol lactone.

The novel process of the present invention is particularly useful for the production of carboxylic ketons suitable for the synthesis of steroids.

The term lower alkyl, as used herein, refers to an alkyl group containing from 1 to 6 carbon atoms. The term carboxylic acyl group, as used herein, refers to an acyl group containing up to about 12 carbons derived from substituted or unsubstituted carboxylic acids. Typical acyl groups include acetyl, trifiuoroacetyl, trichloroacetyl, propionyl, butyryl, diethylacetyl, benzoyl, cyclopentylpropionyl, adamatoyl, trimethylacetyl, phenylacetyl, undecenoyl, and the like.

The following examples are provided to illustrate the present invention. Unless otherwise stated, temperature is centigrade and proportions are parts by weight.

EXAMPLE 1 4 0A: 4 OAc R In the above formulas, R is a defined above, R is methyl, ethyl or propyl and Ac is hydrogen or a carboxylic acyl group.

To a solution of 1 g. of dimethyl methylpho'sphonate in 30 ml. of dry tetrahydrofuran under nitrogen and cooled to 78", there is added one equivalent of n-butyl lithium in hexane with stirring. After about 10 minutes at 78", one equivalent of the tricyclic enol lactone (I) (R is methyl; Ac is benzoyl) in 35 ml. of dry tetrahydrofuran is added. The reaction mixture is allowed to rise to room temperature and stand for about two hours. The reaction mixture is diluted with water and extracted with ether. The ether extracts are combined, washed with water, dried and evaporated under reduced pressure to give the tricarbocyclic ketone (III) (R is methyl; Ac is benzoyl) which can be further purified by chromatography, if desired.

The tricarbocyclic ketone (III) can be used to prepare therapeutically useful 19-nor or A -steroids using the procedure of, for example, U.S. Pat. 3,150,152.

The tricyclic enol lactone of Formula I can be obtained according to the procedure of French Pat. 1,359,675 (1964) or Velluz et al., Tetrahedron, Suppl. 8, Part II, pp. 495-505 (1966,) and references cited therein.

The process of Example 1 is repeated with the exception of using dimethyl ethylphosphonate in place of dimethyl methylphosphonate and there is obtained the v n-unsaturated tricarbocyclic ketone of Formula IV (R is methyl; Ac is benzoyl) EXAMPLE 2 To a solution of 4 g. of diethyl 4,4-ethylenedioxypentylphosphonate (V) (R is ethyl) in 50 ml. of dry monoglyme under nitrogen and cooled to about -80, there is added one equivalent of n-butyl lithium in hexane with stirring. After about five minutes at 80, one equivalent of the tricyclic enol lactone (I) (R is methyl; Ac is benzoyl) in 75 ml. of dry monoglyme is added and the reaction mixture allowed to rise to room temperature. The reaction mixture is allowed to stand for about 2.5 hours and then diluted with water. The mixture is extracted with ether and the ether extracts combined, washed, dried and evaporated under reduced pressure to give the tricarbocyclic ketone (VI) (R is methyl; Ac is benzoyl) which can be further purified by chromatography on alumina.

in 60 ml. of dry tetrahydrofuran is added and the mixture stirred for minutes at 0 and allowed to stand 16 hours at room temperature. The mixture is then heated under reflux for three hours, cooled and filtered. The filtrate is concentrated under reduced pressure and the concentrate taken up in ether. This mixture is shaken with saturated aqueous sodium chloride and then separated. The organic layer is separated and concentrated under reduced pressure to give diethyl 4,4-ethylenedioxypentylphosphonate (V) (R is ethyl) which is purified by distillation in vacuo (B.P. 115 at 0.05 mm.).

By using other phosphites, e.g. dimethyl phosphite, dibenzyl phosphite or diphenyl phosphite, in place of diethyl phosphite in the above procedure, the corresponding di-substituted phosphonates are obtained.

6 EXAMPLE 3 OAc OAc 4 R4 (VII) (VIII) To a suspension of 2 g. of dimethyl methylphosphonate in 50 ml. of dry tetrahydrofurau at 78 under nitrogen, there is added one equivalent of n-butyl lithium in hexane with stirring. After about five minutes, there is added one equivalent of bicyclic enol lactone (VII) (R is methyl; Ac is benzoyl) in 50 ml. of dry tetrahydrofuran while maintaining the temperature at about 78. The reaction mixture is allowed to warm to room temperature and to stand at room temperature for three hours. The reaction mixture is diluted with water and then extracted with ether. The ether extracts are combined, washed, dried and evaporated under reduced pressure to give the bicarbocyclic ketone (VIII) (R is methyl; Ac is benzoyl) which can be further purified by chromatography or fractional distillation.

The o e-unsaturated bicarbocyclic ketone of Formula VIII is a valuable intermediate for the synthesis of steroids using the method of, for example, Whitehurst et al., US. Pat. 3,317,566.

The bicyclic enol lactone of Formula VII can be prepared using the following procedure.

A mixture of 0.3 ml. of Z-methylcyclopentane-l,3-dione, 0.33 ml. of methylacrylate and 0.1 g. of potassium tbutoxide in 200 ml. of t-butanol is allowed to stand at about 20 C. for 72 hours. The reaction mixture is Washed with water, dilute sodium hydroxide and then Water to neutral, dried and evaporated to give Z-methyl-Z-(fl-carbomethoxyethyl)cyclopentane-1,3-dione which was purified by distillation.

The above prepared diketoester is then hydrolyzed to the acid by treatment with 1% potassium carbonate in warm methanolzwater (1:1) for eight hours. A total of 5 g. of this acid is mixed with 50 ml. of acetic anhydride containing 2 g. of anhydrous sodium acetate and the mixture boiled for five hours. The acetic 'anhydride is then removed by distillation in vacuo to furnish a residue which is poured into water and extracted with ethyl acetate. The ethyl acetate extracts are combined, washed neutral with water, dried and evaporated. Purification of the resulting residue by vacuum distillation affords 1.2 g. of the enol lactone (VII"):

(VII") A mixture of 5 g. of the diketoester (VII'), ml. of tetrahydrofuran and 1.3 molar equivalents of lithium tri-tbutoxyaluminum hydride is heated at reflux until the hydride reagent is consumed. The reaction mixture is cooled, diluted with concentrated aqueous sodium sulfite solution and the resulting clear supernatant decanted and evaporated. The resulting residue is purified by chromatography on alumina to furnish 1.3 g. of the following alcohol:

which is converted into the corresponding benzoate by treatment with benzoyl chloride in pyridine. The methyl ester is hydrolyzed to the acid which is then cyclized by the procedures described above to furnish the enol lactone of Formula VII (R is methyl; Ac is benzoyl).

By using Z-ethylcyclopentane-l,3-dione and 2-propylcyclopentane-l,3-dione in place of 2-methylcyclopentane- 1,3-dione in the above procedure, the corresponding enol lactones wherein R is ethyl and propyl, respectively, are obtained.

EXAMPLE 4 The process of Example 3 is repeated with the exception of using an equivalent amount of the phosphonate of Formula IX (R is ethyl; R is hydrogen; R and R are methyl and Ac is benzoyl) in place of dimethyl methylphosphonate and the substituted bicarbocyclic ketone (X) (R is hydrogen; R and R are methyl and Ac is benzoyl) is obtained.

CH CH (OR) In the above formulas, Ac, R and R are as defined hereinabove, R is hydrogen or a lower alkoxy of 1 to 6 carbon atoms and R is a lower alkyl of 1 to 6 carbon atoms.

By using other phosphonates of Formula IX in the above process, the correspondingly substituted a ti-unsaturated bicarbocyclic ketone of Formula X is obtained.

The phosphonates of Formula IX can be obtained by using an equivalent amount of the bromide (XI) in place of the ethylene ketal of 1-bromopentan-4-one in the procedure set out in Example 2. The bromide (XI) can be prepared from the corresponding acid by the following procedure.

Ten grams of m-methoxycinnamic acid in 100 ml. of ethanol is hydrogenated with 0.5 g. of pre-reduced 10% palladium-on-charcoal until the uptake of hydrogen ceases. The catalyst is removed by filtration and the filtrate evaporated to yield 3-(m-methoxyphenyl)propionic acid.

A solution of g. of the foregoing priopionic acid in 100 ml. of tetrahydrofuran is added cautiously to a boiling solution of 250 ml. of tetrahydrofuran containing 3 g. of lithium aluminum hydride. The reaction mixture is refluxed overnight with stirring and then cooled and the excess of hydride decomposed by the cautious addition of ethyl acetate and then saturated sodium sulfate. The resulting clear solution is decanted and dried over sodium sulfate. The solvent remaining is removed by distillation to give 3-(m-methoxyphenyl)propauol which is purified by distillation in vacuo. One gram of this propyl alcohol in 50 ml. of benzene is boiled with a slight excess of phosphorus pentabromide until thin layer chromatography no longer indicates the presence of starting alcohol. The reaction mixture is cooled, washed with Water and dilute sodium carbonate solution, dried over sodium sulfate and concentrated to dryness to give 3-(mmethoxyphenyl)propionyl bromide (XI) (R is hydrogen; R is methyl) which is purified by distillation.

R30 CHz-CHg-CHz-Br By using 3,5-dimethoxycinnamic acid in place of mmethoxycinnamic acid, the bromide (X1) in which R is methoxy and R is methyl is obtained.

The bicarbocyclic ketones of Formula X above can be converted into estra-1,3,5(1-0),8,14-pentaenes by treatment with p-toluenesulfonic acid in benzene or by the method of U.S. Pat. 3,317,566. The thus-obtained estra- 1,3,5(10),8,14-pentaene can be converted into therapeutically useful steroids by known procedures, see for example, U.S. Pat. 3,337,542.

EXAMPLE 5 To a suspension of 4 g. of dibutyl methylphosphonate in ml. of dry monoglyme at about 78 under nitro gen, there is added with stirring one equivalent of n-butyl lithium in hexane. After about 10 minutes, there is added one equivalent of 17fl-acetoxy-4-oxa-androst5en-3-one in 75 ml. of dry tetrahydrofuran while maintaining the temperature at about 78. The reaction mixture is allowed to warm to room temperature and then left to stand for about four hours. The reaction mixture is diluted with water and extracted with ether. The ether extracts are combined, Washed, dried and evaporated to give the testos terone acetate (17,3-acetoxyandrost-4-en-3one) which can be purified by chromatography.

By using diethyl ethylphosphonate in the process of this example, the correspondingly substituted tetracarbocyclic compound is obtained, i.e. 4-methyl testosterone acetate.

. By using other steroidal enol lactones in the above process in place of 17,8-acetoxy-4-oxa-androst-5-en-3-one as the starting material, e.g. 4-oxa-cholest-5-en-3-one, 3- ethoxy-17-oxa-D-homoestra-1,3,5(10),15 tetraen-17-one, 17,20;20,21 bismethylenedioxy-l1fi-hydroxypregn-5-en-3- one, and the like, the corresponding a,fl-unsaturated tetracarbocyclic ketone is obtained, e.g. cholest-4-en-3-one, 3- ethoxyD-homoestra-1,3,5(l0),14-pentaen-17-one, and 17, 20;20,2l-bismethylenedioxy 11,8 hydroxypregn-4-en-3- one.

EXAMPLE 6 CH O o H %o (XI I I To a suspension of 2 g. of dibenzoyl methylphosphonate in 30 ml. of dry tetrahydrofuran cooled to a temperature of about 60 under nitrogen, there is added 1.1 equivalents of phenyl lithium in hexane with stirring. After about five minutes, there is added, while maintaining the temperature at about 60, 0.95 equivalents of angelica lactone (XIII) in 40 ml. of dry tetrahydrofuran. The reaction mixture is allowed to warm to room temperature and then left to stand for about two hours. The mixture is then diluted with Water and the product extracted with ether to give 3-met-hylcyclopent-2-en-lone (XIV) which can be purified by vacuum distillation.

By using a mono-substituted methylphosphonate, for example, diethyl ethylphosphonate in the above process, the corresponding Z-su-bstituted a, 3-unsaturated cyclopentone is obtained, e.g. 2,3dimethylcyclopent-Z-en-l-one.

EXAMPLE 7 To a solutionof 5 g. of dimethyl methylphosphonate in ml. of dry tetrahydrofuran cooled to about -78 under nitrogen, there is added with stirring one equivalent of n-butyllithium in hexane. After about 10 minutes, there is added one molar equivalent of 3- methoxy-l6-oxaestra-1,3,5(10),8,14-pentaen-17-one in dry tetrahydrofuran while maintaining the temperature at about 78. The mixture is allowed to warm to room temperature and then left to stand at room temperature for five hours. The mixture is diluted with Water and then extracted with ether. The ether extracts are combined and concentrated to furnish a residue which is chromatographed on neutral alumina eluting with benzene to alford 3-methoxy-l4fl-estra-1,3,5(10),8,l5 pentaen- 17 one and 3-methoxy-14a-estra-1,3,5(l0)8,l5-pentaen- 17-one which can be further purified by recrystallization from aqueous methanol.

0.5 g. of 3-methoxy-14a-estra-1,3,5(l0),8,l5-pentaen- 17-one in 25 m1. of ethanol is reduced catalytically with 50 mg. of 5% palladium-on-charcoal until a molar equivalent of hydrogen is taken up. The catalyst is filtered oil and the filtrate evaporated to dryness to yield the known 3-methoxyestra-1,3,5(l0),8-tetraen 17 one which can be converted into estrone methyl ether by procedures outlined in Chemistry & Industry (London), 1022 (1960) or into l9-nor-A -steroids using the procedure of, for example, US. Pat. 3,318,922.

By repeating the above process using other 16-oxa steroids of the Formula XV, e.g. 3-methoxy-l5-methyl-16- xa-estra-1,3,5(l0,6,8,14 hexaen 17 one as the tetracyclic enol lactone starting material, the corresponding steroidal ketone (tetracarbocyclic .ketone) of the Formula XVI is obtained, e.g. 3-methoxy-15-methyl-14m-estra-L3, (10,6,8,15 hexaen 17 one and 3 methoxy 15- methyl 14B estra 1,3,5(),6,8,l5-hexaen-l7-one.

(XVI) The process of Example 2 is repeated with the exception that the phosphonate employed is a phosphonate of Formula XVII and there is obtained the substituted tricar bocyclic ketone (XVIII) which is useful in the synthesis of valuable 2-methyl-19-nor steroids and 2- methylandrostene steroids using the procedure of, for example, Velluz et al., ibid.

0 3 fi cn -c-cn-cn -cn -n (OR)2 (XVII) r 2 CH2 CHCH o cr-r The mono-substituted methylphosphonates of Formula XVII can be prepared by the procedure described in Example 2 using the ethylene ketal of 1-bromo-3-methylpentan-4-one as the starting material. This bromide starting material can be prepared according to the following procedure.

A mixture of 0.5 mole of 1-acet0xypentan-4-one and 0.5 mole of piperidine in benzene is refluxed using a water separator until no more water distills from the reaction mixture. The reaction mixture is then cooled, washed and dried to afford the 4-piperidyl-l-acetoxypent- 3-ene (XIX). A mixture of 5 g. of XIX in ml. of dioxane is treated with an excess of methyl iodide at 20 C. for 18 hours and then heated at 70 C. for six hours. The reaction mixture is concentrated to a small volume, diluted with water and 1-acetoxy-3-methylpentan-4-one isolated by extraction with ethyl acetate. A mixture of 0.5 g. of this ketone, 100 mg. of p-toluenesulfonic acid, 3 ml. of ethyleneglycol and 100 m1. of benzene is refluxed using a water separator for 24 hours. The reaction mixture is cooled and then 100 ml. of ethanol and 2 g. of potassium hydroxide are added. This mixture is refluxed for six hours, cooled, diluted with water and the corresponding ethylene ketal is isolated by extraction with ethyl acetate. A solution of 0.1 mole of the ketal in 50 ml. of dimethyl'formamide containing 0.1 mole of triphenylphosphine is reacted with 0.1 mole of carbon tetrabromide at room temperature for 18 hours. The mixture is diluted with water and extracted with ether. The ether extracts are combined, washed with water, dried and evaporated. The residue is chromatographed on 400 g. of alumina eluting with hexane-benzene and benzene to give the ethylene ketal of 1-bromo-3-methylpentane-4- one.

EXAMPLE 9 A mixture of 10 g. of 1-chloropentan-4-one, 100 ml. of ether and 1 g. of lithium aluminum hydride is allowed to stand at 20 C. for 20 hours. The reaction mixture is diluted with water and separated. The organic phase is washed with water, dried and evaporated to give 1- chloropentan-4-ol which is purified by distillation. Two ml. of dihydropyran is added to a solution of 1 g. of lchloropentan-4-ol in 15 ml. of benzene. About 1 ml. is removed by distillation to remove moisture and 0.4 g. of p-toluenesulfonic acid is added to the cooled solution. This mixture is allowed to stand at room temperature for four days and is then washed with aqueous sodium carbonate solution and water, dried and evaporated to yield 4- (tetrahydropyran-2'-yloxy)-l-chloropentane which is subjected to the procedure described in Example 2 to give the phosphonate (XX).

The process of Example 2 is repeated with the exception that the phosphonate of formula XX (R is ethyl) is used in place of the phosphonate (V) (R is ethyl) and there is obtained the tricarbocyclic ketone (XXI) which can be 1 I converted into 19-nor steroids described hereinabove, see for example, Example 2.

EXAMPLE 10 To a suspension of 4 g. of diethyl (4-chloropentyl-3- enyl)phosphonate in 50 ml. of dry monoglyme at about 78, there is added 1.1 equivalents of butyl lithium in hexane with stirring under nitrogen. After about 10 minutes, there is added 1.1 equivalents of the tricyclic enol lactone (I) (R is methyl; Ac is benzoyl) in 60 ml. of dry monoglyme while maintaining the temperature at about 78. The reaction mixture is allowed to warm to room temperature and then left to stand at room temperature for about two hours. The reaction mixture is diluted with water and then extracted with ether. The ether extracts are combined, washed, dried over magnesium sulfate and evaporated under reduced pressure to afford the 0:,fl-UI1S3tUI2It6d tricarbocylic ketone (XXII) (R is methyl; Ac is benzoyl) which can be purified further by chromatography on aluminia.

(XXII) The tricarbocyclic ketone (XXII) is a useful intermediate for the synthesis of valuable 19-nor steroids using known procedures such as described in US. Pats. 3,050,550, 3,019,252 and 3,150,152.

The phosphonate used in the process of this example can be prepared according to the following procedure.

A mixture of 10 g. of 1-bromopentan-4-one, 100 ml. of carbon tetrachloride and 5 g. of phosphorus pentachloride is refluxed for hours. The reaction mixture is then cooled, washed with dilute sodium carbonate and Water, dried over magnesium sulfate and evaporated to give 1- bromo-4-chloropent-3-ene which is purified by distillation and converted into the phosphonate by the procedure described in Example 2.

EXAMPLE 11 To a suspension of 4 g. of diethyl 4,4-dimethoxybutylphosphonate in 50 ml. of dry monoglyme at about -70 under nitrogen there is added one equivalent of phenyl lithium in hexane with stirring. After about five minutes, there is added 1.0 equivalent of the bicyclic enol lactone (VII) (R is ethyl; Ac is benzoyl) in 50 ml. of dry monoglyme while maintaining the temperature at about 70. The reaction mixture is allowed to warm to room temperature and then allowed to stand at room temperature for 3.5 hours. The reaction mixture is then diluted with water and extracted with ether. The ether extracts are combined, washed, dried over magnesium sulfate and evaporated under reduced pressure. The residue is chromatographed on silica gel to afiord the 8- unsaturated bicarbocyclic ketone (XXIII) (R is ethyl; Ac is benzoyl).

A mixture of 1 g. of the above bicarbocyclic ketone, 25 ml. of dioxane and 1 ml of 5% aqueous HCl is boiled 15 minutes. The reactiori mixture is allowed to cool, poured into water and the resulting mixture separated. The organic phase is evaporated to dryness to furnish the corresponding aldehyde which is taken up in 20 ml. of acetone, cooled to 0 C. and a slight molar excess of Jones reagent (prepared by mixing 26 g. of chromium trioxide with 23 ml. of concentrated sulfuric acid and diluting with water to ml.) Upon completion of the oxidation as followed by thin layer chromatography, the reaction mixture is diluted With water and then extracted with ethyl acetate. The ethyl acetate extracts are combined, washed with water, dried and evaporated under reduced pressure to afford the acid (XXIV) (R is ethyl; Ac is benzoyl) which is a valuable intermediate for the synthesis of known 19-nor-A and A -Steroids useful as therapeutic agents using the procedure of, for example, Belgium Pa-t. 629,251 (1963); 'French Pat. 1,465,400 (1965) or Velluz et al., idib.

4 OAC 4 OAc coon OCH

CH 3 on (XXIII) (xxrv) Z/ 2 2 in 100 ml. of benzene is added and the mixture stirred overnight followed by refluxing for two hours. The reaction mixture is cooled, washed with water and purified by vacuum distillation to give fi,p-dimethoxyethylmalonic acid diethyl ester. A mixture of 5 g. of this ester in 100 ml. of ethanol containing 5 'g. of sodium hydroxide is heated under reflux until evolution of carbon dioxide ceases. The reaction mixture is then saturated with carbon dioxide and evaporated to dryness under vacuum. The residue is suspended in 50 ml. of dry dimethylformamide to which is added a large excess of methyl iodide. The reaction mixture is stirred at room temperature for about 24 hours and then poured into water. The resulting mixture is extracted with ether and the ether extracts combined, washed with water and evaporated to give 4,4- dimethoxybutyric acid methyl ester which is purified by distillation. A mixture of 4 g. of this methyl ester, 50 m1. of dry tetrahydrofuran and 1.1 equivalents of lithium aluminum hydride is refluxed overnight. The reaction mixture is allowed to cool and then filtered with water. This mixture is extracted with ether and the ether extracts are combined, washed, dried and evaporated to dryness to afford 4,4-dimethoxybutanol A solution of 0.1 mole of 4,4-dimethoxybutanol in 50 ml. of dirnethylformamide containing 0.1 mole of triphenylphosphine is allowed to react for 18 hours with 0.1 mole of carbon tetrabromide. The mixture is diluted with Water and extracted with ether. The ether extracts are combined, washed with water, dried and evaporated to a crude product which is purified by distillation to yield 4,4-dimethoxybutylbromide. This bromide is then converted into the diethyl phosphonate using the procedure described in Example 2.

EXAMPLE 12 The process of Example 11 is repeated using a phosphonate (XXV) as the phosphonate reagent and n-butyl lithium as the base and the corresponding carbocyclic ketone (XXVI) is obtained which can be converted into valuable 6-methyl steroids.

OOAc 4 (XXVI) Conversion of the carbocyclic ketone (XXVI) into 6- methyl steroids can be accomplished by, for example, catalytic reduction using 5% palladium-on-charcoal in ethanol to the intermediate (XXVII) which is converted into the free acid (XXVIII) using the procedure described in Example 11. The free acid can then be cyclized to the tricyclic enol lactone (XXIX) using the method of Velluz et al., ibid. The enol lactone (XXIX) can then be treated as described in Example 1 and 2 to obtain the corresponding tricarbocyclic ketone which can be converted into 6-methyl steroids using the procedures referenced therein.

cs CH 1 o ej (a c CH en o c n c a on n; CH cu BZ (xxvrr) 3k (xxvrrr) (xxrx) EXAMPLE 13 Diethyl methylphosphonate (1.94 g.) suspended in 50 ml. of dry tetrahydrofuran is treated with 1.1 equivalents of butyl lithium in hexane under nitrogen at about 7 8. After 10 minutes, one equivalent of benzalphathlide in 10 ml. of tetrahydrofuran is added while maintaining the temperature at about 78. The reaction mixture is allowed to warm to room temperature and then left to stand at room temperature for three hours. The reaction mixture is diluted with Water and then extracted with ether. The ether extracts are combined, washed with water, dried and the solvent removed under vacuum. The residue is chromatographed on silica eluting with methylene chloridezhaxene (4:1) to afford 3-benzylind-2-en-1- one and a small amount of starting material.

EXAMPLE 14 The process of Example 3 is repeated with the exception that the phosphonate (XXX) (R is ethyl) is used in place of dimethyl methylphosphonate and there is obtained the substituted bicarbocyclic ketone (XXI) (R is methyl; Ac is benzoyl).

4 OAc (XXXI) (XXXII) The phosphonate (XXX) can be prepared using the following procedure.

A mixture of 0.5 mole of 1,3-dithiane and 300 ml. of tetrahydrofuran cooled to 30 is treated with 0.5 molar equivalents of 1.5 molar n-butyl lithium in hexane under nitrogen and stirred for 15 hours at 20. Then 0.5 mole of the tetrahydropyranyl ether of 3-bromopropanol in 200 ml. of tetrahydrofurau is added slowly with stirring at 5 and then left for 14 hours at 0 under nitrogen. The resulting mixture is cooled to 30 and treated with an additional 0.5 molar equivalents of 1.5 molar n-butyl lithium in hexane. After 1.5 hours, 0.5 mole of 4-chlorol-bromopent-3-ene in 200 ml. of tetrahyrofuran is added. The reaction mixture is left standing for 18 hours at 0 and then allowed to Warm to room temperature for four hours. Water is added and the resulting mixture extracted with ether. The ether extracts are combined, washed with water, dried and concentrated. The resulting dialkylated thiane (XXXIII) is dissolved in methanol and stirred for two hours with 20 ml. of 1% oxalic acid solution. The reaction mixture is poured into water containing an excess of sodium carbonate solution and then extracted with ether to afford the corresponding free hydroxy compound. The free hydroxy compound is dissolved in dry ethylene glycol containing 0.5 g. of mercuric chloride. This reaction mixture is allowed to stand overnight and then heated to 60 for five hours. After cooling, water is added and the ketal (XXXIV) isolated by extraction with ether. A mixture of 2 g. of the ketal and 30 ml. of methylene chloride: pyridine (2: 1) is cooled to 70 and then treated with one equivalent of tosylchloride in methylene chloride. The mixture is left standing at 0 for 18 hours and then allowed to warm to room temperature. The mixture is then diluted with water and the resulting tosylate isolated by extraction with methylene chloride and purified by chromatography on deactivated alumina. This tosylate (0.5 g.) in 25 ml. of acetone is refluxed for 24 hours with 0.5 g. of sodium iodide. After cooling, the reaction mixture is diluted with water and extracted with ether. The

(xxxrn) EXAMPLE 15 The process of Example 2 is repeated using as the phosphonate reagent, the phosphonate of Formula XXXV (R is ethyl) and there is obtained the tricarbocyclic ketone (XXXVI) (Ac is benzoyl) which can be converted into l9-nor steroids or androstane steroids by methods disclosed in the Journal of American Chemical Society, 82, #21, 5464 (1967).

an i-6 2 PM 04 (icon! The phosphonate (XXXV) can be obtained according to the following outlined procedure.

CO CH COCl CH I 3 Ten grams of the isoxazole (1) is heated at reflux with 200 ml. of 1% sodium hydroxide in methanol for five hours. The reaction mixture is then acidified to pH 3 with HCl and the acidified mixture is then concentrated to a small volume under reduced pressure. Water is added and the acid isolated by extraction with ethyl acetate. The crude acid (9 g.) is taken up in methanol and treated with one equivalent of sodium methoxide. The alcohol is evaporated and the residue dried under reduced pressure.

' The residue is then suspended in dry benzene and treated at 0 C. with an excess of oxalyl chloride. After the evolution of gas ceases, the reaction mixture is allowed to warm to room temperature and the excess of oxalyl chloride removed by evaporation of the solvent medium to dryness. The resulting acid chloride (2) is taken up in benzene and treated with an excess of ethereal diazomethane. After the formation of the diazoketone is com plete, the ether is removed and the resulting diazoketone heated under reflux in octane-Z-ol until nitrogen evolution ceases. The crude product is purified by distillation and reduced with an excess of lithium aluminum hydride in 200 ml. of tetrahydrofuran under reflux. The reaction mixture is decomposed by cautious addition of ethyl acetate and the inorganic salts precipitated by the addition of concentrated sodium sulfate solution. The solution is then filtered and evaporated to yield the alcohol (5) which is purified by distillation. The alcohol (5) is then treated with phosphorus tribromide in benzene to give the bromide (6) which is converted into the phosphonate (XXXV) by the procedure described in Example 2.

EXAMPLE 16 r a M n It!) 2 J ciu -r (010 I c R30 2 4:3 R 0 cz-r ca (mull (xXXvIII) The process of Example 3 is repeated with the exception that dimethyl methylphosphonate is replaced with an equivalent amount of the phosphonate (XXXVII) (R is ethyl; R is hydrogen; R is methyl) and the corresponding substituted age-unsaturated bicarbocyclic ketone ()O(XVIII) is obtained.

The bicarbocyclic ketones of Formula XXXVIII are excellent intermediates for the production of valuable 7- methyl steroids using the procedures described in Ex ample 4.

The phosphonates of Formula XXXVII can be prepared according to the following outlined procedure wherein R R and X are as defined hereinabove.

\ (XXXVII) A solution of 0.6 mole of the aldehyde (7) and 0.5 mole of methyl a-bromopropionate in ml. of dry benzene is added dropwise to 0.6 mole of zinc dust. After 15 ml. of the solution is added, the mixture is heated to initiate the reaction. The remaining portionof the solution is then added during one hour. The resulting mix ture is cooled, washed with water, dried and then refluxed with 0.2 g. of p-toluenesulfonic acid for five hours. After cooling, the reaction mixture is washed with dilute sodium bicarbonate solution and water and then dried and purified by distillation to give 8. One gram of 8 in 25 ml. of ethanol is hydrogenated with 0.1 g. of 5% palladium/carbon catalyst until 1 molar equivalent of gas is taken up. The catalyst is filtered off and solvent evaporated to give 2-methyl-3-(substituted phenyl)propionic acid methyl ester. One gram of this ester in ml. of tetrahydro'furan is reduced with 2 g. of lithium aluminum hydride until thin layer chromatography indicates the absence of starting ester. The reaction mixture is cooled, treated cautiously with an excess of ethyl acetate followed by saturated sodium sulfate solution. The organic layer is decanted oif, dried with sodium sulfate and evaporated to give the alcohol (9) which is converted into the corresponding halide or tosylate (10) by procedures described herein (see Examples 4, 8 and 14). The halide or tosylate (10) is then converted into the phosphonate (XXXVII) using the procedure described in Example 2.

1 7 EXAMPLE 17 In the above formulas, R and Ac are as defined hereinabove.

EXAMPLE 18 The process of Example 3 for the preparation of the bicyclic enol lactone (VII) is repeated with the exception that trifluoroacetyl chloride, acetyl chloride, and trimethylacetyl chloride is used in place of benzoyl chloride and there is obtained the corresponding carboxylic esters of VII, that is, the trifluoroacetate, acetate and trimethylacetate.

What is claimed is:

1. A phosphonate represented by the formula:

wherein R is monocyclic aryl, alkyl having from one to eight carbons, cyclohexyl, benzyl, methoxyethyl or ethoxyethyl and R is 0 CH3-LH-CHFCHQ- 2'. A phosphonate of claim 1 wherein R is lower alkyl.

No references cited.

NORMA S. MILESTONE, Primary Examiner U.S. Cl. X.R.

260586 R, 586 H, 488 B, 476 C, 950, 951, 956, 340.9, 307 R, 590, 327 M, 473 R, 343.2 R, 294.3 A, 612 R, 612 D UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 39,428 Dated February 1, 1972 Inventor(s) John Fri d It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

I Column 3, lines 29-32, that portion of formula (A' j reading "CH should be CH Column 9, line 27, "l, 3,5 (l0, 6,8, 14" should read l, 3,5 (10) 6,8, 14 and line 32 "5 (10,6,8, 15" should read 5(10) ,6,7, 15

Column 13, line 74, (XXI) should read (XXXI) Signed and sealed this 18th day of July 1972.

(SEAL) Attest:

EDWARD M.FLETCI-IER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

